Because of phonological processes, the actual realisation of /i/ after alveolar consonants (⟨д⟩, ⟨з⟩, ⟨л⟩, ⟨н⟩, ⟨р⟩, ⟨с⟩, ⟨т⟩, or ⟨ц⟩) is retracted to a close central unrounded vowel[ɨ] or [ʷi], after labials: ⟨б⟩, ⟨в⟩, ⟨м⟩, ⟨п⟩.

In Rusyn, it denotes a sound a bit harder than [ɨ] and close to the Romanian sound î, also written â. In some situations, it may occur after palatalised consonants (синьый "blue", which never happens in Russian), and it often follows ⟨к⟩, ⟨г⟩, ⟨ґ⟩ and ⟨х⟩.

While vowel letters in the Cyrillic alphabet may be divided into iotated and non-iotated pairs (for example, ⟨а⟩ and ⟨я⟩ both represent /a/, the latter denoting a preceding palatalised consonant), ⟨ы⟩ is more complicated. It appears only after hard consonants, its phonetic value differs from ⟨и⟩, and there is some scholarly disagreement as to whether or not ⟨ы⟩ and ⟨и⟩ denote different phonemes.

Like many other Cyrillic letters, it was originally from a ligature: ꙑ, formed from Yer⟨ъ⟩ and ⟨і⟩ (formerly written either dotless or with two dots) or Izhe (⟨и⟩ which formerly resembled ⟨н⟩). In mediaeval manuscripts, it is almost always found as ⟨ъі⟩ or ⟨ъи⟩. Once the letters ⟨ъ⟩ and ⟨ь⟩ later lost their values as vowels in the Slavic languages, the current simplified form ⟨ы⟩ evolved.

The letter Yery in several fonts

The letter is usually romanised into English and most other West European languages as ⟨y⟩: Krylov (family name, Крылов). However, ⟨y⟩ may be used for other purposes as well (such as in digraphs). That spelling matches Polish, which uses ⟨y⟩ to represent the same sound. Russian ⟨ы⟩ is used to transliterate Polish ⟨y⟩ into Cyrillic: Maryla – Марыля.

Native Russian words do not begin with ⟨ы⟩ (except for the specific verb ыкать, "to say the ⟨ы⟩-sound″), but many proper and common nouns of non-Russian origin (including some geographical names in Russia) beginning with the letter exist: Ytyk-Kyuyol (Ытык-Кюёль), Ygyatta (Ыгыатта), a village and a river in Sakha (Yakutia) Republic respectively, or Eulji Mundeok (Ыльчи Мундок), a Korean military leader.

In the Ukrainian alphabet, the sound [ɨ] is denoted by ⟨и⟩, and the letter ⟨ы⟩ is not used in Ukrainian. Ukrainian ⟨и⟩ usually is transcribed in Russian as ⟨ы⟩.

The letter ⟨ы⟩ is also used in Cyrillic-based alphabets of several Turkic and Mongolic languages (see the list) and denotes a darker vowel [ɯ]. Corresponding letter in Latin-based scripts is ⟨б⟩ (dotless I).